10 Keys for Successful Esthetic-Zone Single Immediate Implants
Robert A. Levine, DDS; Jeffrey Ganeles, DMD; Luiz Gonzaga, DDS, MS; Joseph Y. Kan, DDS, MS; Harry Randel, DMD; Chris D. Evans, BDSc, MDSc, MRACDS; and Stephen T. Chen, BDS, MDSc, PhD, FRACDS
The 10 keys for successful esthetic-zone single immediate implants encapsulate in an evidence-based manner the treatment planning and replacement of single hopeless teeth in the maxillary anterior sextant. These include 2 treatment-planning, 5 surgical, and 3 prosthetic keys, which, collectively, aim to minimize soft- and hard-tissue complications for an optimal esthetic implant restoration. The straightforward, advanced, and complex (SAC) classification was designed to aid clinicians in the treatment planning of dental implant cases. Cases are stratified by the degree of surgical and restorative risk and complexity for both the surgical and prosthetic phases of treatment. Based on the 10 keys, the management of an immediate implant in the esthetic zone is considered a complex SAC procedure. As described in this article, a complex SAC procedure requires careful patient selection and treatment planning, along with precise execution by skillful clinicians, to achieve successful results.
The straightforward, advanced, and complex (SAC) classification system1 was developed to aid clinicians in the treatment planning of dental implant cases. Treatment of a single-tooth replacement in the esthetic zone is considered a complex procedure requiring a team approach.2 This is because once an esthetic complication occurs, restoring the lost hard and soft tissues to their original presurgical levels is extremely difficult.3-6
According to Levine et al,4 immediate placement in the esthetic zone requires the clinician to be experienced and knowledgeable about esthetic diagnosis, minimally invasive extraction techniques, oral plastic-surgical procedures (eg, hard- and soft-tissue grafting, “gummy smile” correction/crown lengthening), and accurate 3-dimensional (3D) implant placement and restoratively driven planning/placement based on cone-beam computed tomography (CBCT) analysis. Tissue-contour management requires prosthetic knowledge of provisionalization techniques to sculpt peri-implant tissue for developing submergence contour from the implant shoulder to the mucosal zenith to adequately support the tissue. Final impression techniques must capture and transfer this submergence contour, or “transitional zone,” to be duplicated in the final crown.
In a 2009 systematic review, Chen et al6 suggested potential risk for facial gingival recession of was up to 30% of cases if inclusion criteria were not used for immediate implant placement. They identified preexisting defects of the facial bone, thin facial bone, thin soft-tissue biotype, and facial malposition of the implant as potential risk factors for gingival recession following immediate single-tooth implant placement.
Recent systematic reviews by Levine et al4 and Chen et al3 and consensus statements by Morton et al5 were written to organize the diagnosis, planning, and treatment of single-tooth implants in the esthetic zone, along with the treatment of complications associated with them. Their conclusions3-5 suggested that a team protocol, if strictly followed, would provide high predictability in preventing esthetic complications related to single-tooth implants, and they proposed guidelines to ensure high success rates.
Since 2014, various studies have reported on the expansion of specific indications and techniques for immediate placement and restoration of implants in the esthetic zone. Outstanding short- and medium-term results have been achieved that are comparable with staged or delayed placement7-19; however, none of these more recent publications were included in the aforementioned 2014 systematic reviews,3,4 and they represent newer information and a somewhat different perspective. The purpose of this article is to identify 10 essential elements for performing immediate single-tooth replacement in the esthetic zone in adult patients with long-term, successful outcomes. This treatment procedure is defined as complex under the SAC classification and requires careful patient selection and treatment planning, as well as precise execution by skillful clinicians, to achieve successful results.
10 Keys Defined
The 10 keys are as follows:
1. Esthetic risk assessment (ERA). Each patient’s case is reviewed so his or her specific esthetic risk criteria for immediate placement in the esthetic zone can be determined.
2. Tomographic plan. CBCT analysis and a restorative-driven treatment plan are performed to assess adequate buccal bony-wall thickness and determine the sagittal root position (SRP) of the tooth, the alveolar form, and the planned implant position.
3. Minimally traumatic tooth extraction. Extraction is performed without flap reflection (if possible) with evaluation of the status of the buccal plate.
4. 3D implant placement in good available bone both apically and palatally along the palatal wall. This will help assure a, preferably, screw-retained provisional and final restoration. Ideally, an anatomically correct surgical guide template (ACSGT) is used.
5. Use of a narrower (3.3 mm to 4.3 mm) implant versus a wider-diameter (4.5 mm or greater) implant. A narrower implant will assure at least a 2-mm- to 3-mm-buccal gap adjacent to the intact buccal socket wall. This can be preplanned with a careful CBCT analysis and an understanding of the restorative-driven plan.
6. Buccal gap bone graft. A low-substitution mineralized bone material (deproteinated bovine bone mineral [DBBM] or freeze-dried bone allograft [FDBA]) is used to bone-graft the buccal gap.
7. Facial gingival grafting. This is done using palatal connective tissue placed in a buccal envelope under the buccal marginal tissue and facial to the intact buccal plate to augment the existing gingiva so that it is thick.
8. Immediate contour management of the emergence profile from the implant. The goal is to preserve the soft-tissue and transition-zone contours using an anatomically correct or slightly under-contoured emergence profile with either a screw-retained immediate provisional or a customizable healing abutment.
9. Custom impression coping technique. Once the team is satisfied with the soft-tissue esthetics developed in the provisional stage, a custom impression coping technique is used to duplicate the transition zone, which is replicated in the final impression and transferred to the laboratory model.
10. Final restoration with a screw-retained crown. If direct-screw retention is not possible, stock abutments should be avoided because it is difficult to remove excess cement from deep interproximal margins. An anatomically contoured customized abutment with a titanium implant interface should be fabricated with the final facial cement line no deeper than 1 mm circumferentially. If cemented restorations are needed, radiopaque cement should be used via a minimum cement load technique (ie, copy abutment technique).
Review of the 10 Keys
1. Esthetic Risk Assessment
Achieving a long-term esthetic result starts with comprehensive planning prior to surgical intervention and a restorative-driven approach1-6,20-24 (Figure 1 through Figure 4). A patient’s pretreatment implant evaluation in the esthetic zone should include an initial consultation to establish a diagnosis and prognosis based on a comprehensive examination of his or her medical, dental, and compliance history. The patient’s periodontal and restorative needs should also be considered. Diagnostic casts and necessary radiographs should include CBCT to evaluate important anatomic landmarks,25,26 skeletal relationships, and bone availability to aid in careful presurgical planning.
Skeletal dimensional stability, even if determined using serial cephalometric radiographs, is not a guarantee of growth cessation, even in adults. Patients should be informed that, despite using the best available prognostic practices, alveolar growth can recur or continue, and changes in restorations may be required in the future.27 Intraoral and extraoral digital photographs documenting the patient’s smile both at rest and in full smile are recommended to determine the lip line in relation to the gingival margins surrounding the tooth to be replaced. The location of the adjacent interproximal papillae should also be documented. These photographs aid in the comprehensive treatment planning of the case and may influence the surgical approach.1-5,28-31
During the presurgical evaluation and consultation, the clinician should also review the ERA (Figure 4) with the patient to establish the overall esthetic risk. This considers the patient’s smile line and esthetic demands, and establishes a comprehensive site analysis of hard- and soft-tissue thickness and width along with the patient’s gingival biotype. Per Yoshino et al8 the gingival biotype is categorized as thin or thick based on visibility of an underlying periodontal probe (SE Probe SD12 Yellow, American Eagle Instruments Inc., am-eagle.com) through the gingival tissues (ie, visible = thin; not visible = thick).
The ERA becomes part of the patient’s record along with the documentation of the discussion. The patient’s surgical and prosthetic concerns regarding the tooth being replaced and adjacent teeth should be included. Restorative modifiers such as cervical tooth shape, adjacent tooth restorative status, parafunctional status, skeletal and occlusal classification, and overbite/overjet relationship should be evaluated in relation to the proposed treatment. Articulated study casts and/or other digital records should be collected to assist with treatment-planning procedures.
2. Tomographic Planning
When placing implants in the esthetic zone, a presurgical CBCT scan provides invaluable information about the site, including the existing buccal plate width, anticipated need for bone grafting, anticipated implant width and length, and SRP (Figure 5). The CBCT information can also help determine if the anticipated implant site will need to be modified with orthodontic therapy or vertical extrusion (forced eruption) for site development.32 Based on limited studies and a general consensus among the scientific community, ideally ≥2 mm of buccal bone labial to the healed implant is considered necessary to ensure proper soft-tissue support and to avoid resorption of the buccal bone and gingival recession following restoration.4,33-35
A CBCT scan is strongly recommended to evaluate the patient’s buccal plate presence, dimension (which may not be visible if it is less than 1 mm thick), and ridge width.36 CBCT data will aid the team in preplanning the case and assessing the need for soft- and/or hard-tissue augmentation37,38 at the time of or prior to implant placement and whether immediate implant placement with immediate provisionalization can be performed. If the clinician has less than 1 mm of buccal bone facial to the root to be extracted, immediate placement might not be the preferred treatment because of increased risk for future tissue loss and recession. Instead, a lower risk treatment option—early implant placement—may be a consideration; it provides the opportunity for significant buccal augmentation using a staged approach.38
In relation to the SRP, Kan et al36 evaluated CBCT images of 100 patient retrospectively and classified the relationship of the SRP of the maxillary anterior teeth (600 samples) to their respective osseous housings (Class 1 to Class 4 categories). They found 81.1% were Class 1 (the root is positioned against the labial cortical plate: favorable for immediate placement), 6.5% were Class 2 (the root is centered in the middle of the alveolar housing without engaging either the labial or palatal cortical plates at the apical third of the root: technique-sensitive for immediate placement), 0.7% were Class 3 (the root is positioned against the palatal plate: technique-sensitive for immediate placement), and 11.7% were Class 4 (at least two-thirds of the root is engaging both the labial and palatal cortical plates: unfavorable or contraindicated for immediate placement).
A CBCT image is useful to evaluate the integrity of the existing facial bone.38-40 A Class 1 socket (no facial dehiscence or fenestrations) is most likely to have an excellent result without significant hard- or soft-tissue changes after immediate tooth replacement. However, some Class 2 (buccal dehiscence or bone loss) defects can be clinically present without associated gingival recession, which could represent complication risks for future recession.40
Assessing both the CBCT information and clinical parameters helps in developing a restoratively driven treatment plan. The final tooth position needs to be determined such that the planned SRP falls within the proposed tooth position with an emergence profile consistent with the appropriate 3D placement of the implant shoulder to avoid procedural placement errors. In cases in which the SRP and final tooth position cannot be correctly determined and achieved without staged augmentation procedures to develop an appropriate bone site, the immediate placement procedure should not be performed due to the high risk for developing a suboptimal result.3-5,38
Immediate implant placement should be considered in selected healthy patients and conducted by highly skilled clinicians with adequate clinical experience and expertise.6,38,41-44
3. Minimally Traumatic Tooth Extraction
Minimally invasive surgical techniques, including the use of anterior surgical forceps and elevators and aids to vertically extract a remaining fractured root, are available and highly recommended (Figure 6 and Figure 7). Overheating of the osteotomy site or trauma to adjacent soft-tissue papilla and socket walls should be avoided. If possible, a flapless procedure without any vertical releasing incisions is preferable. In addition, once the tooth is removed and the socket walls degranulated, creating multiple bleeding points in the socket is recommended to promote a more rapid vascularization of the graft material. Piezosurgical devices using copious amounts of sterile solution can be used for sectioning fractured roots and creating fine bleeding points.30,43 Confirmation of an intact buccal and palatal wall is necessary to proceed with immediate implant placement.
4. Platform-Switched Implant Along Palatal Wall
When immediate single-tooth implant placement is anticipated, a platform-switched implant is recommended8,13-15,38,43 (Figure 7 and Figure 8). Surgical placement should be completed with minimal trauma to the surrounding soft and hard tissues. The implant osteotomy point is directed along the palatal wall using an ACSGT to facilitate palatal or cingulum trajectory to enable (if practical) a screw-retained provisional restoration.
The buccal-lingual placement of the implant is critical to the final position of the facial gingival margin. Two studies45,46 evaluated facial soft-tissue recession and found a strong association between increased recession and a buccal position of the implant. Implants with a facially positioned shoulder showed three times more facial gingival recession than implants with a palatally positioned shoulder. The use of an ACSGT and manufacturer-specific bone profile drills (utilized along the palatal wall) aids the surgeon in maintaining the correct buccolingual position of the implant without the implant migrating facially during insertion.
Implant placement depth should be referenced from the anticipated final midfacial mucosal zenith of the planned final restoration. This will ensure that a gradual prosthetic emergence profile is developed that supports the peri-implant mucosa, is stable long term, and can be cleaned by the patient. If the coronal buccal wall is totally intact, the vertical position of the implant shoulder needs to be 1 mm apical to the buccal osseous crest to compensate for the average of 1 mm crestal loss that is normally seen. If bony undercuts are expected apical to the implant, then a tapered-design implant is recommended to avoid a buccal fenestration, which may be more likely to occur with a straight-walled design.47,48
Site preparation is performed using the manufacturer’s twist drills with copious irrigation with cold saline and completed employing an index finger for tactile sense along the buccal plate of bone to confirm no buccal vibration or fenestration.43 With good primary stability as measured by insertion torque greater than 35 Ncm or resonance frequency greater than ~65 RFI and favorable patient conditions and cooperation, an immediate provisional that is out of occlusal contact can be placed. Caution should be taken in placing an immediate provisional in a patient with significant parafunctional habits. Alternatively, a custom-contoured transmucosal healing abutment can be placed, which can be replaced with an esthetic provisional restoration following a conventional healing period of 2 to 3 months.7,11
5. Use of Narrower Implant
Treatment-planning decisions must be made prior to surgery based on CBCT analysis. Buccal bony-wall resorption should be expected following an immediate implant placement. This means that once the implant is inserted into the correct 3-dimensional position along the palatal wall, there should be at least a gap of 2 mm or more facial to the implant to the internal aspect of the buccal wall. This gap, once bone grafted, should be sufficient to prevent future midfacial mucosal recession. (Figure 7 and Figure 8). Often, a reduced-diameter implant affords additional buccal gap room to create a desired 2 mm to 3 mm of space for grafting.19,49,50 Using a wider-diameter implant (ie, ≥4.5 mm width) can have the negative effect of reducing the gap distance to the buccal plate to less than 2 mm to 3 mm and be responsible for future marginal gingival recession, especially if the implant is placed with buccal angulation.19,45,46 Reduced-diameter implants have narrower connections and require slightly deeper placement than standard-diameter implants (ie, 4.1 mm) to allow for the added room to create subgingival contours. Use of an ACSGT aids this critical 3D placement.
Smaller-diameter implants have less surface area than standard-diameter implants and may have correspondingly reduced primary stability. This also may contraindicate immediate provisionalization and should be considered in treatment planning.
The principle of using a reduced-diameter (3.3 mm) versus a standard-diameter (4.1 mm) immediately placed implant in conjunction with grafting the buccal gap with deproteinized bovine bone mineral (DBBM) was shown to promote new bone formation, and it enhanced the level of bone-to-implant contact in dogs.51 Covani et al52 also showed similar results in a dog model using 3.25-mm implants placed to the lingual. Vertical buccal bone resorption was only 0.05 mm51 compared to 2.5 mm in a study by Araújo et al53 in which wider-diameter (4.1 mm) implants were placed.
Chen and Buser31 suggested preparing the osteotomy palatally and avoiding oversized implants to reduce the risk for adverse esthetic outcomes for implants placed in immediate extraction sites. Rosa et al19 proposed a method for selecting the diameter of immediate implants and guiding the placement position of them based on the buccolingual dimension, with the goal of preserving the buccal bone wall. Using pre- and postoperative CBCT images, the socket buccolingual distance was measured to determine the appropriate implant diameter while considering a 3-mm gap to the buccal wall as the surgical goal. The authors suggested maintaining a 3-mm gap between the buccal bone surface of the implant and buccal bone wall offered predictable results in the stability and vascularization of the buccal plate (using tuberosity autogenous bone graft in the gap). In summary, positioning the implant along the palatal wall and maintaining a buccal gap of 2 mm to 3 mm, and possibly using reduced-diameter implants, may be important factors in reducing the rate of vertical and buccal bone resorption and subsequent facial gingival recession.
6. Bone Graft With Low-Substitution Bone Filler
Clinical studies using an immediate implant protocol (type 1 implant placement)2,3,6 in the esthetic zone strongly suggest bone augmentation of the buccal gap is necessary to achieve adequate buccal bony contours, assuming the minimum buccal bone width of 2 mm is valid (Figure 9). This approach will help maintain buccal bony-wall stability over time.7-12,15,16,19,30,38,43,45,46,54-56 When the surgeon is considering type 1 (immediate) implant placement the status of the facial bone should be evaluated for any preexisting defects, because this is a major risk factor for future facial mucosal recession.2-4,38,57 Kan et al57 studied the treatment of vertical buccal wall defects at the time of type 1 immediate implant placement and immediate provisionalization (IIPP). At 1 year, they observed 1.5 mm or greater of facial mucosal recession in more than one-third of the patients receiving treatment with bone grafting of the buccal wall vertical bony defects. The most facial recession noted in this study was when correspondingly larger facial bone defects were encountered. Notably, the study did not use platform-switched implants or other recommendations from the 10 keys mentioned herein, which may also have contributed to poor results.
Januario et al58 analyzed 250 CBCT scans and measured the facial-bone thickness in the anterior maxillae at 1 mm, 3 mm, and 5 mm from the bone crest in 250 patients. They found the bone thickness in almost all tooth sites examined was ≤1 mm thick (≤0.6 mm on average). They also noted in almost 50% of sites, the marginal (5 mm) portion of the wall was <0.5 mm wide. Based on these CBCT-scan studies, it may be concluded that once a maxillary anterior tooth is gone, not only may the entire marginal buccal bone wall be lost, but an additional 2 mm of the original socket dimension may also disappear during healing.34,58-60 Kan et al61 reported ongoing changes in the marginal tissue levels continued to occur up to 8.2 years (mean 4 years) after IIPP without grafting of the buccal gap or use of a subepithelial connective tissue graft (SCTG). In this study, thin biotypes receded three times more than thick biotypes. Four (11%) patients expressed esthetic concerns and were subsequently treated with hard- and soft-tissue grafting procedures to try to improve undesirable esthetic outcomes.